Hi there, I am interested in installing a direct exchange (DX) GSHP in a vertical borehole in my garden. I saw an Earthlinked video where installers braze the U-bend at the end of the copper tubes before they insert it in the borehole. Should I not be worried about leaks, especially at high pressures? Are the seals reliable for conventional GSHP refrigerants? Are they reliable for CO2 refrigerant which requires higher pressures?? Now, let's imagine that the ground loop of copper tube in the ground is somehow seamless and perfectly sealed. Would that mean that we could apply higher pressures to the refrigerant and hence get a higher COP fro the pump, or is this inexact? Thanks and regards fholler

Posted By fholler on 24 Mar 2010 03:22 PM
Would that mean that we could apply higher pressures to the refrigerant and hence get a higher COP fro the pump, or is this inexact?

Suggest you stop worrying about small differences in COP. The differences
in operating cost for fractional improvements in COP are vanishingly small.
And fractional improvements are the best you can hope for -- because the
thermal conductivity of the soil/rock is the limiting factor. In the final analysis,
copper versus HDPE in-ground piping makes very little difference.

...how do you calculate the dollar value of simplicity, reliability, servicibility?

Looby

the test for any connection of any pipe , is if done properly is it stonger then the pipe itself. The answer for any ( copper (when brazed) or hdpe ) is yes .

higher pressures doesnt equal high effeciency, think of it like the oil level in your car , to high or to low is bad for the equipment and the eff.

Any decent installer is very concerned about leaks , all connections should be made by an experienced guy who then pressure tests with either a tracer gas/ gas detector , soap bubbles , or old faithfull a good amount of time

Posted By Looby on 24 Mar 2010 05:19 PM

Posted By fholler on 24 Mar 2010 03:22 PM
Would that mean that we could apply higher pressures to the refrigerant and hence get a higher COP fro the pump, or is this inexact?

Suggest you stop worrying about small differences in COP. The differences
in operating cost for fractional improvements in COP are vanishingly small.
And fractional improvements are the best you can hope for -- because the
thermal conductivity of the soil/rock is the limiting factor. In the final analysis,
copper versus HDPE in-ground piping makes very little difference.

...how do you calculate the dollar value of simplicity, reliability, servicibility?

Looby

I'm with Looby I still maintain your focus is misplaced. Pros and consumers took the time to create a list of what is important when you shop for geo and you continue to inquire about minutae.
j

The brazed joint on the loop before its inserted into the hole is made by the EarthLinked Technologies at their factory. Not that I couldn't braze it just as well...
The loop is then pressurized to approx. 400 psi with Nitrogen. This pressure must hold indefinitely until the loop is placed in the ground. The initial test will reveal if there's a leak. Then, before they are boxed, they're checked again. Then, before a driller puts in into the bore hole, they test to make sure that pressure is still there. If it's not, they better not put it in the ground. That would be very self-defeating, irresponsible, stupid, etc.

As mentioned in posts above, the connections are typically stronger than the contiguous pipe itself.

Basically, that connection should be of no concern--the only concern is that the installer follows manufacturer's recommendations/procedures and does it RIGHT.

For a non-banned refrigerant, EarthLinked uses R-407c.